While it may come off as Narm to some, the look on Boris' face when he gazes up at the grizzly is epically priceless.
Boris in general has plenty of funny lines. A particularly memorable one comes to mind:
Boris: OH, NO! I'M BEGINNING TO UNDERSTAND THE BEAR!
It's even funnier when you watch the sequence leading up to that. After Balto decides to go after Steele and his team, the movie cuts to a goose shaped hole in the snow, indicating that Boris has been trying to talk him out of this crazy stunt for awhile.
Boris: Balto, please, don't go crazy on me now! Ah! (falls, gets back up) This is foolishness! You will die like a dog! Ooh, no offense.(Falls through a hole in a drainage, but continues to yell at Balto before emerging from the pipe and landing on the ice, while Muk and Luk are sliding on the ice right behind him) You will be frozen stiff by morning! When you are big frozen statue named "Balto", don't come running to me! (The bears hit him, taking him down the ice with them, and Luk asks where Balto's going))
Muk: He says-
Boris: (interupting): "Where is he going?" He's going into freezing coldness to find a dog he doesn't like and bring back medicine to a town that doesn't like him! OH, NO! I'M BEGINNING TO UNDERSTAND THE BEAR''!
And when he decides to help Balto, we get this:
Boris: So, let's go get the medicine.
Balto: Wait a minute, now you're coming?
Boris: Spending days in bitter cold, facing wild animals, risking death from exposure (laughs) is like holiday in old country.
In the aftermath of the grizzly fight, when hugging Balto, he gives us this:
Boris: Oh, Balto! I was so scared I got people bumps!
Even funnier, as he muses on Balto and Jenna cuddling together, Luk ruins the moment by shaking himself dry, and the drops fly all over Boris. If Luk smiling innocently and all poofy doesn't make you laugh, Boris' next line will.